1. Field of the Invention
The present invention relates generally to the field of dental implants and in particular to a system of anatomic dental implants, which may be converted to an anatomic facsimile of a natural tooth. The present invention also relates to eliminating the quandary of having to decide if the implant/abutment seam will compromise aesthetics or if the implant/abutment seam will compromise the integrity and long-term of the bone. The present invention also relates to ancillary components and instruments related to the placement and restoration of the anatomic implant.
2. Background of the Invention
A dental implant is an artificial tooth made of metal with a porcelain coating designed to make it look real. Its most important component is its root, a titanium anchor that is surgically implanted into the jawbone, usually by an oral surgeon or periodontal surgeon. Generally, the anchor is implanted alone, without the tooth. Gradually, during a healing period the bone grows around the implant securing it in place. An abutment is added to the implant for the artificial tooth to sit upon and then a replacement tooth or crown is attached to the metal post. Implants can also be used to anchor bridges and permanent dentures when more than one tooth is missing.
The replacement of a patient's tooth or placement of an anchorage fixture for attaching an overlying fixed or removal prosthesis initially consists of the placement of endosseous anchorage implants to which subsequent attachments might be added. Systems as described by U.S. Pat. No. 3,589,011 to Sneer, U.S. Pat. No. 3,797,113 to Brainin, U.S. Pat. No. 3,979,828 to Taylor, U.S. Pat. No. 4,324,550 to Reuther et al., and U.S. Pat. No. 4,416,679 to Mozsary et al., have proven to be successful for the long term anchorage of the endosseous dental implants to the maxillary and mandibular jawbones.
The placement of endosseous dental implants has evolved using 2 surgical approaches. One of these approaches uses a submerged technique where the implant is placed at or below the crest of the bone. The gingiva is closed over the bone and the implant thereby submerging the implant. The other surgical approach involves placement of an implant that extends coronally beyond the alveolar crest where the soft tissue flap is placed around a cover screw extending from the implant body. Once the dental implant has become permanently affixed to the bone by means of the process known as osseointegration, abutment attachments are added to the implant in order to make it suitable for the placement of a prosthetic tooth crown. Those prosthetic teeth crowns are then generally affixed to the abutments by means of fixation screws or by means of permanent cementation. Because the abutment is added to the implant, there is a seam (microgap) between the implant and the abutment. Additionally most implants are manufactured with a polished or smooth machined collar combined with a rough implant body. Studies have shown that the seam (microgap) and the junction of the rough surface and the smooth collar (r/s border) cause crestal bone resorption when placed in close approximation to the crestal bone. Ercoli, U.S. Pat. No. 6,217,333, attempted to address this issue by creating a curved top on the implant so that the seam and the r/s border more closely approximated the saddle-shaped crestal bone. This innovation only partially addressed the issue because the seam (microgap) persisted, though in an altered form; also Ercoli 333 presumed that finite shapes could accommodate the infinite variety of crestal bone shapes. Similarly, Wöhrle, U.S. Pat. Nos. 6,174,167 and 6,283,754 created an implant with a scalloped coating that was designed to remain below, yet follow the crest of bone. Above this scalloped coating there was intended to be a different treatment of the implant surface, such as a machined collar, that was distinctly compatible with the soft tissue. This concept of scalloped exclusion of the collar surface from the subosseous regions because the collar is only compatible with the gum tissue is not in keeping with the technology of the PACE implant, as marketed by Coatoam since 1996 where the surface treatment of the collar is compatible to both bone and tissue attachment. This collar transition does not require a scalloped design because the collar treatment can go below the crest of bone or be above the crest of bone without creating any bone die-back. Additionally there is good gingival attachment to this surface. Also the PACE implant has been marketed since 1996 as being adjustable by the doctor so that the top edge can be scalloped like the pre-fabricated Ercoli 333 design. This ability to adjust the implant provides the property of keeping the treated collar in a subgingival position where it would not retain plaque, plus the property of being able to adjust the implant edge allows for adaptation of the implant when it is surgically placed in the patient's mouth. This is particularly valuable in maxillary anterior teeth where the crest of bone most often is not actually symmetrically scalloped, but rather is much higher on the facial aspect than it is on the interproximal or palatal aspects of the tooth socket. Both Ercoli 333 and Wöhrle 167 & 754 have symmetrical designs, and the implant edge in Ercoli 333 along with the collar in Wöhrle 167 & 754 can end up in a subosseous position on the palatal aspect when the implants are placed in the maxillary anterior area thereby leading to potential bone die-back in these regions.
Because implant abutments are subject to rotational loosening, the dental prosthesis, which is subsequently affixed to the post attachments, is also subject to this unscrewing phenomenon. This can lead to loosening and failure of the dental prosthesis. In order to prevent this phenomenon most implant systems add a non-round interconnection or a Morse taper between the endosseous dental implant and the abutment to prevent rotational movement. In most designs, a screw is then passed through the abutment, affixing it to the body of the implant. This screw generally has a positive seat in some portion of the abutment. Once the screw is tightened with sufficient torque, the abutment is firmly anchored to the dental implant. The coronal extent of the abutment usually has some design feature such as a flat side that ultimately engages the crown prosthesis to provide a non-rotational feature to the cemented crown. In U.S. Pat. No. Des. 401,695 Daftary described a non-round anatomic shape that prevents crown rotation. Rotational forces to the abutment are absorbed at the implant by the non-round component rather than being transmitted directly to the screw itself. These non-round components are generally shaped like a hex, an octagon, a multi-pointed star, or a spline. In each case the seam between the implant and the abutment presents a problem after surgical implant placement because of subsequent bone dieback.
Another type of anti-rotational feature on implants is the non-round anatomically shaped implant. This type of implant was described in U.S. Pat. No. 5,246,370 to Coatoam. In this type of system the crown attaches directly down onto the non-round implant body. Since the edge of the head of the implant is a machined non-round anatomical shape the crown cannot rotate. In these systems the anti-rotational feature is the non-round implant shape of the exit profile. With this type of design it is necessary to set the timing of the implant so that the anatomic shape corresponds to the replaced tooth. It is also necessary to keep the edge of the implant in a position above the crest of bone because even though the crown margin finishes on the implant body, that margin may also act as a microgap that can lead to bone loss. In the application of the Coatoam patent 370, the commercially available PACE implant can be altered so that the bevel at the top edge of the implant can be altered by the doctor to accommodate the infinite variety of shapes of the crestal bone. However, whenever the implant was altered it then became essential for the restorative doctor to take direct impressions of the altered dental implant rather than using available impression transfer posts and implant analogs. In U.S. Pat. No. 5,759,034 Daftary proposed a non-round anatomically shaped implant similar to the 370 Coatoam implant but in 034 Daftary there is still an implant/abutment seam between the crest of bone and the margin of the crown.
There exists a need for an anatomically shaped dental implant that can be placed so that the crestal bone does not die back as a consequence of an implant/abutment seam. Also there is a need to eliminate this potentially weak implant/abutment seam so that smaller implants can be manufactured without having to enlarge the abutment in order to accommodate anti-rotational components and connectors to the implant. Further, there is a need for an anatomically shaped implant where the edge of the margin of the final crown can be variably and infinitely set by the doctor and the laboratory technician as ultimately determined by the shape of the adjacent crestal bone and the junctional gingival epithelium.